Production of conduits



Jam. 29, 1924. 1,481,807

J. F. M URRAY PRODUCTION OF CONDUITE Filed July 5. 1922 "NVENTOR.

TTORNEY.

Patented .lane 29, i924,

Meise? Fries.

TENT- l JOHN F. MURRAY, or BROOKLYN, NEW YORK. l

PRODUCTION or' ooNDUITs.

Y Application ined July e,

To all @0.7mm t 7a2-cry concern Be it known that I, JOHN F. MURRAY, a citizen of the UnitedV States, residing in Brooklyn, N ew Yorlr,'lizive invented certain new and useful Improveinentsii'i the Production ot Conduits, oit which the following is a speciiication. .f

.ln several piioi patents of Thomas E. Murray, partiularly Nos. 1,406,577 and 1,406,578 ot February let, 1922, there are described methods and devices `for molding pipes and similar hollow structures oit plastic material such as cement, and designed particularly for lthe molding of small conduits for carrying electric conductors. The aforesaid patents are based on the use of a core of paperwhich, after the hardening ofthe cement, is collapsed and withdrawn. In certain ont the aforesaid Murray patents (for example No. .1,387 ,066, August 9, 1921) there is described a spiral wire enclosing the core and use-fl to withdraw the core longitudinally from the molded conduit.

The present invention presents an ,iinprovenient upon the schemes described in the aforesaid patents.

The accompanying drawings illustrate embodiments of the invention. Y

Fig. l is a side elevation-ot a coreY with a tube ot concrete shown in section upon the core;

Fig. 2 is an enlarged' sectional vview on the line 2`2 of Fig. l;

Fig. 3 is a vertical section of the tube ot- Fig. l with the core withdrawn;

Fig. et is a vertical section of the core showing the construction at a joint;

Fig. 5 is a plan Oi the same.' The core maybe made ot various ina- Vterials flexible enough to permit withdrawal in the manner hereinafter described butV slt-iii1 enough to hold the tubular shape during Y the molding or the pipe, and preferably still enough to do this without internal support, although various styles of internal support may be provided such' for example as the internal coil of Patent No. 1,387,066 above cited. In the case illustrated the core l `is made of paper wrapped and formed in three plies as indicatedat L", 3 and 4, Fig. 2. This is a common kind ot paper or cardboard tubing.

In combination with this hollow core Iuse a metal strip 5 wound spirally around the core and attached thereto by means ot prongs 6 bent inward along theedges of the .casefthe pulling of ularly in the with spiral oiii ts Y 1922. serial No. 5772,35?.

Vface on the outside and is so thin 'as to be nearly flush with the surface of the core and thus to provide a smooth moldingsurface tor the pipe 7 which is cast around it.

The tube -being molded, the core is with-y drawn by seizing' theprojecting end ot the strip 5 and pulling it strongly. lf anL in ternal support for the core has been used,y

this will, of the paper p itself, but bibulous so as `to absorbwater from the cement and thus` to become softened, itis, ot' course, necessary towait until this softening effect is obtained. ln any course, be first withdrawn. lf

produced veryk used has been suiiiciently stift byV the strip has two teir.

dencies. First, by reducing the diameter of 1 the coil it squeezes the core inward away from the wall of the molded pipe and, even without the prongs, would grip the internal coilrt'rictionally and would carry it or most or it along out of the molded pipe. y Secondly, the direct attachment of the strip to the material of the core pulls the latter along with the'strip and out of the pipe.

It is quite important that the material of the core be completely removed from so that there shall be no ditiiculty in subsequently drawing electric conductors therethrough Or using the pipe in any other way. The spiral strip with its attaching prongs makes it possible to clean the core out of the pipe completely without the use of any special Y appliances and without special diliiculty. Various other means may `be used or attaching the strip positively to the core.

'Anadvantage in the positive attachment of the coil to the core asdistiiiguished from a mere frictional attachment, arises particmaking of a jointbetween successive sections of the core so as to mold a long conduit. This and 5.

Here the strip 5 is made to pass through registering Openings insections l of 'the core and a couplingsection 8 fitting within the abutting ends othecsections '1. The strip passes through'holes in sections l and 8 to the inside of the core and thence.

out through siinilaiOpenings't-o the outside `of the adjoining section l. With an engage- 'ment of this 'sort it will be appreciated that the Vpipev is illustrated in Figs. L`

iio

the pulling of the metal strip will positively pull out the core sections by reason of its attachment to the latter. Various other methods of attachment or of tying the core section 8 in with the strip may be utilized.

rlfhough l have described with great particularity of detail certain embodiments of my invention, yet it is not to be understood therefrom that the invention is restricted to the particular embodiments illustrated. Various modilications thereolt in detail and in the arrangement of the parts may be made by those sltilled in the art without departure from the invention asdelined in the following` claims.

What I claim isl. hollow molding` core of paper in combination with a metal strip attached thereto throughout substantially its tull length and adapted when drawn out ot thc molded object to also withdraw the core.

2. A collapsible and removable hollow molding core in combination with a metal strip attached thereto, the core being of vflexible material adapted to be collapsed and withdrawn from the molded object by means of the metal strip.

3. A hollow molding core in combination with a strip wound spirally around said core and attached thereto.

Ll. A hollow molding core in combination with a metal strip having pointed projo@ tions at intervals entering the material olA the core and fastening the strip thereto.

5. A hollow molding core in combination with a metal strip wound spirally around said core, said strip having a flat smooth outer :tace and having inward projections at intervals entering the material of the core.

6. A hollow moldingcore comprising a plurality ot sections in combination with a metal strip wound around at least one of said sections and passing through two adjacent sections.

7. The method ot' molding tubular articles which consists in providing a collapsible core7 attaching ak metal strip to said core throughout substantially its full length, casting the article and then pulling the strip and by said attachment pulling the core out of the article.

In witness whereof, I have hereunto signed my name.

' JOHN F. MURRAY. 

